IMPROVEMENT OF EVALUATION METHOD FOR ROCK MASS STRENGTH BY NONLINEAR MULTI-SCALE ANALYSIS

改进了基于多尺度分析的非连续岩体强度评价方法。岩体中的结构面如裂隙、节理等被视为薄层，用普通实体有限元模拟，从而可以利用岩体表面的图形图像进行分析。通过一系列石膏砂浆试件的压缩试验，观察到了裂缝闭合的非线性应力-应变关系，并以本构方程的形式给出了它们之间的非线性关系。用非线性本构关系的薄层来表示裂纹，代替复杂的接触分析模型，用刚度的硬化和软化来表示裂纹的非线性闭合和张开行为。因此，仅从裂隙分布的图形图像和完整岩石的力学性质出发，采用薄层模型可以较好地模拟含多裂隙岩体的非线性变形行为。此外，还利用原对偶最优化的公式，发展了一种功能强大的极限载荷分析方法，并将其纳入薄层分析系统。从而形成了非连续岩体非线性多尺度分析系统的原型。对石膏砂浆开裂试件的直剪试验和现场实际岩体剪切试验进行了验证分析。结果与测量相当好，并揭示了多尺度分析系统的有效性。

A strength evaluation method based on the multi-scale analysis for discontinuous rock mass has been improved. Discontinuities in rock mass such as cracks and joints are treated as thin layers and modeled by ordinary solid finite elements, which enables utilization of graphical image of rock mass surface in the analysis. Nonlinear stress-strain relation of crack closing has been carefully observed in a series of compression tests of gypsum mortar specimen, and their nonlinear relation has been formulated in a form of constitutive equation. Cracks are represented by thin layers with the nonlinear constitutive law, instead of complicated contact analysis model, and their nonlinear closing and opening behaviors are expressed by hardening and softening of its stiffness. The nonlinear deformation behavior of rock mass that includes many cracks are therefore appropriately simulated by suing the thin layer model only from graphical image of crack distribution and mechanical properties of intact rocks. In addition, a powerful limit load analysis has also developed by utilizing formulation of the primal-dual optimization and incorporated into the thin layer analysis system. Thus the nonlinear multi-scale analysis system for discontinuous rock mass has been made in a form of prototype. Validation analyses have been done for direct shear test of cracked gypsum mortar specimen and an actual rock mass shearing test in site. Results agreed with measurements fairly well, and revealed the validity of the multi-scale analysis system.